Plant treatment with urea peroxide

ABSTRACT

Compositions comprising urea peroxide are effective for treating plants for fungal, bacterial, and viral infections and for infestations of mites and insects. The compositions reduce populations of ice nucleating bacteria on plants, thus protecting the plants from frost damage. The compositions are applied to the aerial portions of plants, e.g., leaves, flowers, fruits, stems, branches, vines, and trunks.

FIELD OF THE INVENTION

This invention relates to agricultural pesticides, e.g., fungicides andbactericides, and to compositions that protect plants, trees, and vinesfrom frost damage.

INTRODUCTION

Fungi, bacteria, viruses, mites, insects, and other pests are majorcauses of plant damage and crop loss.

Frost also causes serious damage and crop loss. Many plants can survivetemperatures a little below 0° C., e.g., down to about -5° or -10° C.,without serious damage, as long as no ice forms on the plants. Often,however, ice does form at such temperatures and plants suffer frostdamage. For ice to form at such temperatures, heterogeneous ice nucleimust be present to initiate crystallization of supercooled water. Whenfewer ice nuclei are present, less ice forms and less damage occurs tothe plants. Bacteria present on the plants play a role in frost damageby acting as ice nuclei. Two species of bacteria that have beenassociated with ice nucleation and frost damage to plants arePseudomonas syringae and Erwinia herbicola.

SUMMARY OF THE INVENTION

It has now been found that urea peroxide is effective for inhibiting ordestroying plant pests, such as fungi, bacteria, viruses, mites, andinsects, when applied to aerial portions of plants. Frost protection isobtained through destruction of ice nucleating bacteria.

DETAILED DESCRIPTION OF THE INVENTION

Urea peroxide comprises one or more adducts of urea and hydrogenperoxide. It can be made by crystallization from an aqueous solution ofurea and hydrogen peroxide and is available commercially from a numberof sources. The most common form of urea peroxide is the 1:1 molaradduct of urea and hydrogen peroxide. Adducts having 2 and 4 moles ofhydrogen peroxide per mole of urea have been reported and can be used.The 1:1 adduct is preferred for use in the practice of this invention.Mixtures of the various adducts can also be used.

Solid urea peroxide and solutions thereof are preferably stabilized bythe addition of a stabilizer. Suitable stabilizers are described in U.S.Pat. Nos. 3,629,331, 3,912,490, and 4,155,738, all of which areincorporated herein by reference.

Urea peroxide can be applied directly to the aerial portions of plants,i.e., any portion of the plant above the soil or growing medium, such asleaves, flowers, fruits, branches, stems, vines, crowns, and trunks.Urea peroxide is believed to act directly upon the pest to be controlledand is therefore preferably applied to the vicinity occupied by thepest.

Urea peroxide can be formulated for application in ways similar to thoseused for other topical plant treatments. The urea peroxide can beapplied in solid form, e.p., as a dust, usually in combination with asolid carrier/diluent such as clay, talc, or the like; or as asuspension in a nonsolvent liquid carrier such as a light oil.

Urea peroxide can also be formulated and applied in solution. It isbelieved that urea peroxide, i.e., the urea-hydrogen peroxide adduct,dissociates to some extent in certain solvents, e.g., water, with theextent of dissociation being inversely related to the concentration ofthe solution. Furthermore, it is known that urea peroxide can beprepared by crystallization from a solution of urea in concentratedhydrogen peroxide. When a solution containing urea and hydrogen peroxidein a volatile solvent such as water is applied to a plant, for exampleby sprayinq, the solvent will normally evaporate quickly. This resultsin progressively higher concentrations of urea and hydrogen peroxide inthe remaining solvent until at some point the urea-hydrogen peroxideadduct can form. Therefore, the term "composition comprising ureaperoxide" as used herein with reference to solutions refers both (a) tosolutions in which at least a portion of the urea-hydrogen peroxideadduct remains intact and (b) to solutions containing urea and hydrogenperoxide. Solutions used in the practice of this invention arepreferably made by dissolving urea peroxide in the chosen solvent. Lesspreferably, the solutions can be made by dissolving urea and hydrogenperoxide in the solvent, by dissolving either component in a solution ofthe other, or by mixing separate solutions of urea and hydrogenperoxide. Mixtures of solvents can also be used.

The urea peroxide adduct crystallizes in definite molar ratios of ureato hydrogen peroxide, most commonly 1:1, although 1:2 and 1:4 adductshave also been reported. Compositions having different ratios of urea tohydrogen peroxide can be prepared by adding additional urea or hydrogenperoxide to a composition comprising an adduct, by mixing adducts ofdifferent ratios, or by dissolving varying proportions of urea andhydrogen peroxide in a solvent. Beneficial results can be obtained withcompositions having molar ratios of urea to hydrogen peroxide rangingfrom about 1:50 to about 50:1. Preferably, the ratio is between about1:25 and 25:1, more preferably between about 1:10 and 10:1, and evenmore preferably between about 1:5 and 5:1. A molar ratio of 1:1 is mostpreferred.

Compositions of the invention are low in biuret, a phytotoxic chemicaloften occurring as a byproduct in the manufacture of urea. Preferably,the biuret content is less than about 2 percent, more preferably lessthan about 1 percent, based on the weight of urea peroxide. Mostpreferably, the compositions are essentially biuretfree.

A wide variety of fungal and bacterial plant pests can be controlled inaccordance with this invention. For example, Phytoohthora species suchas p. parasitica, P. citroohthora, and P. cinnamomi, alone with othersof the family Pythiaceae and the order Peronosporales, are a major groupof fungal pathogens on a wide variety of crops. Three different types ofdiseases are caused by this species: foliar, flower, and fruit diseases;systemic stem, crown, and root diseases; and local diseases on roots,hypocotyl, or crown. Some of the diseases are devastating, and the costsfor the chemical control of these pests represent about one-third of thetotal fungicide market. Other genera of common fungal tests includePythium, Monilinia, the powdery and downy mildews, rusts, and smuts.

In accordance with this invention, plants can be protected from frostdamage by treating the aerial portions thereof, particularly tenderportions such as leaves, flowers, fruits, and soft stems, with ureaperoxide so as to reduce the population of, or inhibit the growth of,ice nucleating organisms, e.g., bacteria, thereon. This inventionprovides the greatest protection from frost damage under thosecircumstances where ice nucleating organisms are a significant factor inthe occurrence of frost damage, i.e., at temperatures between about 0°and about -10° C., preferably between about 0° and -5° C. At highertemperatures, of course, ice does not form. At lower temperatures, icecan form whether ice nucleating organisms are present or not. Inaddition, plants vary in their hardiness to cold and freezing. Thus, theembodiments of this invention directed to frost protection are of thegreatest value in the treatment of plants susceptible to damage fromicing at temperatures down to about -10° C., preferably down to about-5° C.

Usually, plants are treated in anticipation of freezing temperatures,e.g., when frost-inducing conditions are predicted by a weatherforecasting agency, since the ice nucleating organisms will slowlyreestablish themselves after the plants are treated. Desirably, plantsare treated no more than 2 weeks before frost-inducing conditions occur,preferably no more than 1 week before, and more preferably no more than2 days before. Emergency treatment can be made at any time before icehas formed on the plants, even during the night when a frost advisoryhas been issued.

Both healthy plants and those which are already infected or infestedwith a pest can be treated in accordance with this invention. Forexample, healthy plants having otherwise-harmless (i.e., non-pathogenic)ice nucleating bacteria on their foliage can be treated for frostprotection.

All plant varieties, including fruiting and principally vegetativevarieties, can be treated in accordance with this invention. Fruitingplants, for purposes of this invention, include plants that bear anyvariety of produce other than vegetative growth, such as annual andperennial vegetables, fruits, nuts, grains, fiber crops, and theflowering plants. Plants grown primarily for their vegetativeproductivity, such as wood cross and the wide variety of grasses grownfor animal feeds and decorative purposes, can also be treated inaccordance with the methods of this invention.

All varieties of vegetables can be treated, including lettuce, broccoli,cauliflower, asparatus, onions, cabbages, celery, rhubarb, artichokes,tuberous crops such as potatoes, turnips, rutabagas, sugar beets, andpeanuts, tomatoes, beans, bell peppers, chili peppers, eggplants, okra,etc. Illustrative of fruits that can be treated in accordance with thisinvention are peaches, apples, citrus, avocados, cherries, grapes(varietal and table), strawberries, raspberries, bananas, etc. Treatablenut crops include walnuts, pecans, almonds, cashews, etc. Essentiallyall grains can be treated, including corn, wheat, sorphum, maize, rice,barley, oats, etc. Illustrative animal feed crops and grasses includealfalfa, bermuda, rye, and bluegrass. Illustrative fiber cross includecotton, hemp, kenaf, and flax. All wood crops can be treated inaccordance with this invention, including both hardwoods and conifers,such as oak, elm, maple, walnut, spruce, hemlock, alder, loblolly pine,redwood, mahogany, cypress, cedar, Douglas fir, and white pine.Flowering plants that can be treated include all varieties of domesticand commercially grown flowers, such as orchids, roses, chrysanthemums,azaleas, camellias, carnations, pansies, snapdragons, etc.

Urea perooxide compositions can be applied at a broad range of rates,depending on the plant being treated, the pest to be controlled,temperature, humidity, the concentration of urea peroxide in thecomposition, and the like. In general the compositions are applied at arate of at least about 0.1 pounds urea peroxide equivalent per acre,usually at least about 1 pound, preferably at least about 5 pounds, andmore preferably at least about 10 pounds per acre, Useful applicationrates can exceed about 1000 pounds urea peroxide per acre. Preferably,application rates are less than about 500 pounds per acre, morepreferably less than about 250 pounds per acre, and most preferably lessthan about 150 pounds per acre.

An aqueous solution suitable for spraying can contain, for example, atleast about 1 pound, preferably at least about 5 pounds, more preferablyat least about 7.5 pounds of urea peroxide per 100 gallons of water;usually, the solutions contain less than about 100 pounds of ureaperoxide per 100 gallons of water, preferably less than about 50 pounds,and more preferably no more than about 30 pounds per hundred gallons ofwater.

Spray volumes in the range of about 5 to about 200 gallons per acre aresufficient to afford adequate coverage and spray distribution foressentially all plant types except large shrubs and trees, for whichvolumes in that range of about 400 to about 1000 gallons per acre can berequired. Spray volumes of about 5 to about 100 gallons per acre areusually adequate for most agricultural cross, and spray volumes of about10 to about 60 gallons per acre are suitable for the treatment of rowcrops and nursery plants.

Urea peroxide is quite soluble in water, and solutions containingseveral hundred pounds per hundred gallons of water can be prepared.Such concentrated solutions may be too strong to apply directly tofoliage but can be applied to the woody portions of plants, such as thetrunks and branches of trees and shrubs, when strong pesticidal, e.g.,fungicidal or bactericidal, activity is desired.

Solutions for spraying can also contain a suitable surfactant or wettingagent to enhance coverage. Any conventional surfactant that will notdegrade or be degraded by urea peroxide can be used, such as Triton X-77from Rohm and Haas. Surfactants can be used in concentrations rangingfrom about 0.01 to about 10 percent, typically from about 0.1 to about 5percent, preferably from about 0.2 to about 4 percent.

In one embodiment of the invention, for example, an aqueous solutioncontaining about 7.5 to about 30 pounds of urea peroxide per 100 gallonsof water can be applied to citrus trees at a rate of about 400 to about1000 gallons per acre for frost protection.

In another embodiment of the invention, an aqueous solution containingabout 10 to about 20 pounds of urea peroxide per 100 gallons of watercan be applied to strawberries at a rate of 50 to 100 gallons per acrefor frost protection.

In another embodiment of the invention, tomato plants can be dusted witha solid composition containing urea peroxide at a rate of about 10 toabout 60 pounds, e.g., 50 pounds, of urea peroxide per acre forfungicidal treatment.

While particular embodiments of the invention have been described, itwill be understood that the invention is not limited thereto, since manyobvious modifications can be made. It is intended to include within thisinvention any such modifications as will fall within the scope of theappended claims.

I claim:
 1. A method of protecting a plant from frost which comprisesapplying to an aerial portion of said plant, said aerial portion havingan umber of ice nucleating organism thereon, sufficient urea perooxideto reduce the number of said ice nucleating organisms.
 2. The method ofclaim 1 wherein the ice nucleating organisms comprise bacteria.
 3. Themethod of claim 1 wherein the urea peroxide is a solid.
 4. The method ofclaim 1 wherein the urea peroxide comprises less than about 2 percentbiuret by weight.
 5. The method of claim 1 wherein the urea peroxide hasbeen dissolved in a solvent.
 6. The method of claim 5 wherein thesolvent is aqueous and at least about 1 pound of urea peroxide per 100gallons of water has been dissolved therein.
 7. The method of claim 6wherein at least about 5 pounds of urea peroxide per 100 gallons ofwater has been dissolved in the solvent.
 8. The method of claim 6wherein at least about 7.5 pounds of urea peroxide per 100 qallons ofwater has been dissolved in the solvent.
 9. The method of claim 8wherein up to about 30 pounds of urea peroxide per 100 gallons of waterhas been dissolved in the solvent.
 10. A method of protecting a plantfrom frost damage which comprises applying a composition comprising ureaperoxide to said plant when frost-inducing conditions are predicted,said plant having ice nucleating sites thereon.
 11. The method of claim10 wherein the ice nucleating sites comprises microorganisms.
 12. Themethod of claim 10 wherein the ice nucleating sites comprise bacteria.13. The method of claim 10 wherein the composition comprises solid ureaperoxide.
 14. The method of claim 10 wherein the composition comprisesdissolved urea perooxide.
 15. The method of claim 10 wherein thecomposition comprises urea and hydrogen perooxide.
 16. The method ofclaim 10 wherein the composition comprises an aqueous solutioncontaining at least about 1 pound of urea perooxide per 100 gallons. 17.The method of claim 10 wherein the composition comprises an aqueoussolution containing at least bout 5 pounds of urea peroixide per 100gallons.
 18. A method of protecting a plant from frost damage whichcomprises applying to said plant, prior to the occurrence offrost-inducing conditions, a composition comprising urea peroxide. 19.The method of claim 18 wherein frost-inducing conditions occur within 2weeks after application of the composition.
 20. The method of claim 18wherein frost-inducing conditions occur within 10 days after applicationof the composition.
 21. The method of claim 18 wherein frost-inducingconditions occur within 5 days after application of the composition. 22.The method of claim 18 wherein frost-inducing conditions occur within 2days after application of the composition.
 23. The method of claim 18wherein frost-inducing conditions occur within 1 day after applicationof the composition.
 24. The method of claim 18 wherein the compositioncomprises less than about 2 percent biuret by weight of urea peroxide.25. The method of claim 18 wherein the composition comprises less thanabout 1 percent biuret by weight of urea peroxide.
 26. The method ofclaim 18 wherein the composition is essentially biuret-free.
 27. Themethod of claim 18 wherein the composition is aqueous and at least about1 pound of urea peroxide per 100 gallons of water has been dissolvedtherein.
 28. The method of claim 27 wherein at least about 5 pounds ofurea peroxide per 100 gallons of water has been dissolved in thecomposition.
 29. The method of claim 27 wherein between about 7.5 poundsand about 30 pounds of urea peroxide per 100 gallons of water has beendissolved in the composition.